On 11/17/2020 6:06 PM, Arlen Holder wrote:
> The goal is to learn how to diagnose a P0421 using an OBDII scanner.
>
> Request for diagnostic advice to pinpoint least expensive solution
> to resolve persistent P0421 OBDII DTC given...
>
> 1. College kid's early 2000s Mitsubishi fails OBD-only smog
> 2. Neighbor asks me to help out (as if I know anything, which I don't)
> 3. However, I can borrow the vehicle & run live tests via OBDII scanner
>
> Question is, what do I look for in terms of "live data" to help diagnose?
>
> DETAILS FOLLOW:
> o 180K miles, circa 2003 or 2004 model year (I think)
> o Service Engine Soon has been reported to be on for a year

This is easy to diagnose. You just sell that POS and get a newer one.
You know better, Arlen dear. Dumb kid won't graduate anyway. That is
why I married you.